Ostarine (MK-2866): Before and After Results, Dosage, Side Effects

What is Ostarine?

Ostarine is a second-generation selective androgen receptor modulator (SARM), also referred to as:

• Enobosarm
• MK-2866

The objective of ostarine’s formulation and other SARMs is to mimic the anabolic effects of steroids without the harsh side effects. This potential outcome can ensure a safer and more efficacious treatment for patients suffering from:

• Cachexia
• Osteoporosis
• Anemia

What Are the Origins of Ostarine?

GTx, Inc., a US biotechnology firm, first described and developed MK-2866 in 2001. Since then, phase 1, 2, and 3 clinical trials have evaluated the SARM.

In phase 3 trials, GTx announced that ostarine was unsuccessful in the treatment of breast cancer patients suffering from cachexia.

This failure was due to insignificant improvements in muscular strength, despite increases in muscle hypertrophy.

This has led GTx to cease its pursuit of ostarine for the treatment of cachexia. However, the biotechnology company remains committed to modifying MK-2866 for improved success in the future.

Is Ostarine FDA-Approved?

Given its recent creation, the Food and Drug Administration (FDA) has not approved ostarine for human use. Additionally, sporting organizations have prohibited its use for athletic purposes, such as:

• World Anti-Doping Agency (WADA)
• U.S. Anti-Doping Agency (USADA)
• International Olympic Committee (IOC)

It is also illegal to administer ostarine for cosmetic use, with only scientific research permitted.

Such legislation has led to SARM manufacturers modifying their marketing strategy, labeling products as research chemicals instead of dietary supplements, effectively capitalizing on this opportunity.

Travis Tygart, CEO of the United States Anti-Doping Agency (USADA), has stated that he is looking at “legislative options” to remove ostarine and other SARMs from the market.

What Are the Benefits of Ostarine?

• Muscle size and strength
• No virilization in women
• Fat loss

Muscle Size and Strength

Ostarine works like anabolic steroids by activating the androgen receptor, increasing bone and muscle strength. Ostarine also enhances satellite cell cycle activation, resulting in the fusing of myofibers and increasing myonuclei in the muscles.

Because ostarine only affects certain tissues, it can build lean muscle without the androgenic side effects of anabolic steroids. This prevents benign prostatic hyperplasia (BPH) from occurring.

In one study involving elderly men and women, participants increased their lean body mass by 3% after consuming 3 mg/day of ostarine for 12 weeks (1). This is the equivalent of an 80 kg (176 lb) man gaining 2.4 kg (5.3 lb) of muscle.

Given that the prescribed dosage of 3 mg/day is only a fraction of the dose weightlifters typically administer to improve their body composition, these results are encouraging.

The elderly men and women also experienced significant increases in muscular strength, adding 22 lb to their bench press by the 12th week.

No Virilization in Women

Women are particularly vulnerable to virilization effects when taking steroidal compounds. Nonetheless, we have found ostarine to be well tolerated in this context. Elderly women in the above-cited study also experienced no masculinization effects.

Fat Loss

Ostarine is an efficacious SARM for cutting because it can increase insulin sensitivity, which leads to subcutaneous and visceral fat loss.

The reduction of visceral fat is a unique attribute of ostarine, in contrast to various anabolic steroids, which can increase visceral fat. This characteristic elucidates why some steroid users develop a distended waistline, an indication of elevated visceral fat levels.

Thus, ostarine users can experience fat loss throughout the body, particularly in the midsection, reducing overall waist circumference.

Ostarine also possesses positive metabolic effects, increasing calorie expenditure and satiety. Thus, it has direct and indirect lipolytic effects.

In the elderly study, users experienced a 0.6 kg (1.3 lb) reduction in fat mass. We have observed additional fat loss in non-elderly users on ostarine when combined with:

• Standard weightlifting
• Cardiovascular exercise

Thus, being sedentary may inhibit fat loss on ostarine.

Disclosure: We do not permit any form of advertising on Inside Bodybuilding. We monetize our practice through doctor consultations and meticulously selected supplement recommendations, which have yielded significant outcomes for our patients.

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What Are the Side Effects of Ostarine?

• Testosterone suppression
• Liver toxicity
• Cholesterol issues
• Gynecomastia and water retention
• Hair loss

Dr. Mike Israetel says that SARMs in general have “comparable side effects” to anabolic-androgenic steroids. However, he adds that some SARMs, such as ostarine, may be “safe” and “effective.”

Ostarine does not appear to cause hypertrophy of the prostate; however, it does reproduce several anabolic steroid side effects. Therefore, further clinical research is required before ostarine can be regarded as safe for humans.

Testosterone Suppression

The men in the cited elderly study who took 3 mg/day of ostarine for 12 weeks experienced minimal fluctuations in their serum testosterone levels. Some of our patients utilizing more substantial dosages of ostarine, including 25 mg/day, have reported the following:

• Standard libido
• Nocturnal erections
• Increased testicular volume

However, in other users, ostarine can cause low testosterone levels post-cycle, with it negatively affecting the hypothalamic-pituitary-testicular axis (HPTA) due to excessive stimulation of the androgen receptors.

Thus, based on existing research, it is reasonable to conclude that ostarine has no significant effect on endogenous testosterone levels when taken in conservative dosages. However, in elevated dosages, ostarine exhibits a notably suppressant effect, which may not invariably result in perceivable side effects.

Ostarine is widely regarded as a mild SARM based on existing research; therefore, a complete shutdown of the HPTA is unlikely.

Dr. Nicholas Downey states that in rodents, luteinizing hormone and follicle-stimulating hormone levels remain largely “unaffected” by ostarine. However, he adds that prolactin “may be an issue” in sensitive users utilizing ostarine, due to it being a weak antagonist of the progesterone receptor.

Liver Toxicity

In the elderly study, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) liver markers increased above standard levels in 20% of participants, indicating ostarine’s hepatotoxic potential.

Although AST and ALT levels did not rise to a dangerous level, these participants only received a fraction of the dose compared to those who use ostarine for physique-enhancing purposes.

The oral administration of ostarine, which must bypass the liver before becoming fully active, contributes to its hepatotoxicity.

We have found that other SARMs, such as LGD-4033 and RAD-140, also have the potential to cause hepatocellular-cholestatic liver injury, which has been reported in research (2).

Cholesterol Issues

Taking 3 mg/day of ostarine for 12 weeks led to a 27% reduction in high-density lipoprotein (HDL) cholesterol.

This study’s modest dosage and the consequent alterations in cholesterol raise concerns about ostarine’s potential cardiotoxicity.

Thus, ostarine may increase the risk of myocardial infarction in the short or long term, even in modest doses.

The oral nature of ostarine and other SARMs could be related to their adverse effects on:

• HDL cholesterol
• Low-density lipoprotein (LDL) cholesterol

This is due to SARMs stimulating hepatic lipase in the liver upon entry, an enzyme known for decreasing HDL and increasing arterial plaque.

Gynecomastia and Water Retention

Several SARMs can elevate estrogen indirectly via binding to the androgen receptor. This leaves additional testosterone free and available to convert to estrogen.

Consequently, some of our patients have reported experiencing bloating or gynecomastia when using SARMs, despite the aromatase enzyme not being present. However, on ostarine, we commonly observe a dry appearance in the muscles with minimal extracellular fluid.

Furthermore, improved insulin sensitivity on ostarine also indicates its minimal effect on estrogen, thereby reducing the likelihood of experiencing:

• Gynecomastia
• Water retention
• Increased abdominal fat

Hair Loss

A few of our patients have reported hair loss or recession during an ostarine cycle, despite the 5-alpha reductase enzyme not being present. The main culprit behind androgenetic alopecia is elevated dihydrotestosterone (DHT) levels.

Increases in DHT occur indirectly as ostarine competes with users’ natural testosterone when binding to the androgen receptor. In this instance, ostarine is the more potent substance, causing surplus free testosterone to convert to DHT.

Although incidents of hair loss on ostarine are infrequent compared to anabolic steroids, androgenetic alopecia remains possible in our experience.

Ostarine Before and After 45 Days

The Reddit user’s results were achieved by taking 20 mg/day of ostarine for 45 days, combined with:

• Conventional weight training methods
• A balanced diet

The user lost 3 kg (7 lb), yet he appears increasingly muscular. The change is due to enhanced muscle definition rather than increased hypertrophy.

Therefore, the scales may not accurately reflect results when taking ostarine due to the simultaneous effects of muscle building and fat loss.

Before and after pictures are thus crucial when monitoring progress pre- and post-cycle.

We find this user’s results to be above average. Coincidentally, he was training more regularly on ostarine, which may have contributed to a portion of the added muscle tissue and fat loss.

Ostarine Before and After 5 Weeks

This Reddit user lost 13 lb after cycling ostarine for 6 weeks. He administered:

• 12.5 mg/day during week 1
• 25 mg/day for the remaining 5 weeks

He did not report any obvious side effects; however, checkups with a physician are advised to rule out possible deteriorations in health or fluctuations in hormones.

He experienced a notable amount of fat loss, accompanied by increases in muscle fullness and vascularity.

Eating in a calorie deficit may have contributed to a portion of the fat loss experienced during his transformation.

He believes ostarine did not aid him in accumulating muscle mass but likely contributed to muscle retention during his cycle. His strength levels remained stable throughout his 6-week cycle.

Ostarine Before and After 8 Weeks

This Reddit user lost 23 lb after administering 20 mg/day for 8 weeks.

He adopted a calorie-deficit diet during his cycle, contributing to substantial fat loss. He does not appear to have added any marked muscle mass, despite vast improvements in muscle definition.

His strength levels did not increase. However, he credits ostarine for preserving muscle hypertrophy and strength while consuming fewer calories (1,800 per day).

In terms of side effects, he reported:

• High liver enzymes (ALT score: 57 IU/L)
• Low testosterone levels post-cycle (270 ng/dL)

After transitioning into a hypogonadal state, he was eligible for prescribed testosterone replacement therapy. He reported physiological and psychological decline post-cycle, including:

• Feeling jaded
• Experiencing diminished well-being
• Low energy

This is despite the individual not reporting “a high” throughout the ostarine cycle.

We have found ostarine’s results to be comparable to a mild Anavar or Winstrol cycle, with muscle hypertrophy and fat loss occurring synergistically. These three compounds also share similar side effects.

Ostarine Dosage

Ostarine does not have established dosage guidelines due to a lack of FDA approval. However, clinical studies have successfully administered daily doses of:

• 3 mg
• 9 mg
• 18 mg

Those taking ostarine to enhance their body composition commonly take 10–30 mg/day. Women often take the lower end of this range, being 10 mg/day, in a bid to avoid virilization effects.

Higher dosages of ostarine are believed to further promote muscle hypertrophy, making them efficacious during a lean bulking cycle. Lower dosages primarily enhance fat loss, making them more appropriate for cutting cycles.

However, higher ostarine dosages can exacerbate side effects, including:

• Cholesterol values
• Liver values
• Testosterone suppression

Ostarine Cycle

A typical ostarine-only cycle we see is 20 mg/day for 8 weeks. This is utilized by our patients primarily for:

• Fat loss
• Muscle retention
• Strength gain

Men commonly execute the cycle above, whereas women typically administer 10 mg/day for 4–8 weeks.

Individuals can cycle ostarine for up to 12 weeks in some cases. However, this extension is only felicitous if cholesterol, liver, and testosterone values have not excessively deteriorated from the first 8 weeks.

Ostarine can be cycled with other SARMs simultaneously; however, this methodology is not advised due to further elevations of blood pressure and liver enzymes.

Ostarine and Cardarine Cycle

• Ostarine: 20 mg/day for 8 weeks
• Cardarine: 20 mg/day for 8 weeks

Some users commonly stack ostarine with cardarine for more prominent fat loss during cutting cycles.

Cardarine is not a SARM but a peroxisome proliferator-activated receptor delta (PPARD) agonist. Cardarine has a positive effect on:

• Insulin sensitivity
• Fatty acid oxidation

Research has found cardarine to significantly decrease adipose tissue, both in animal and human studies (3).

A randomized controlled trial has shown cardarine to have cardioprotective properties, increasing HDL cholesterol levels (4) and thus potentially reducing elevations in blood pressure from ostarine.

However, Dr. Thomas O’Connor has observed hepatotoxic effects from cardarine based on his observation of patient labs in over 2,000 SARM users. He likens cardarine’s adverse effects on the liver to taking 50 mg/day of Anavar. Thus, stacking cardarine with ostarine can exacerbate liver values, in our experience.

Since cardarine first appeared in scientific research in 2001, its side effects are still unclear.

A concern with cardarine is its carcinogenic risk (5), with long-term animal studies demonstrating an indisputable correlation between its use and various cancers.

The fitness community has criticized these studies for using excessively high dosages. However, even the smallest cardarine dosage proved to be carcinogenic. Consequently, the safety of cardarine is uncertain, leading to the discontinuation of clinical trials in 2009.

How to Administer Ostarine

Ostarine typically comes as an oral solution, dosed at 25 mg/mL, and is taken by mouth.

1. Measure the dose with an eyedropper or syringe.
2. Place liquid in the mouth.
3. Allow the liquid to sit under the tongue for 10–15 seconds before swallowing.

Sublingual administration allows the liquid to contact and penetrate the mucous membrane, creating a more direct and expeditious entry into the bloodstream (6). This placement also inhibits presystemic metabolism, increasing ostarine’s biological availability.

Ostarine is commonly available in capsule form, with 10 mg typically present in each capsule.

Ostarine Reviews: What Are Researchers Observing?

Researchers in our Facebook group have published the following ostarine reviews.

I was extremely suppressed after 8 weeks of 20 mg of ostarine. You may not need a PCT, but always have your PCT on hand before you start this. I did this same stack 8 weeks ago, and I felt tremendous with very positive results.

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Ostarine is my favorite SARM. In my personal experience, I have tried 10 mg/day to 50 mg/day, and I believe 25 mg is the optimal dose. I suggest getting bloodwork before you start and when you are done. I ran maybe 8 or 9 cycles with no suppression whatsoever, but my last cycle shut me down completely, and my PCT failed to restart my balls. Consider looking into GW-501516 or GW-0742, as ostarine can negatively impact your cholesterol ratio (but these compounds do a phenomenal job helping to regulate that while promoting fat loss and energy). Ostarine is pretty liver toxic, so I strongly suggest 1,200 mg/day of NAC (and/or TUDCA) to mitigate the elevation in AST and ALT you may experience.

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I ran ostarine at 50 mg per day and felt like rubbish. Worse than any other SARM. Everyone is different, though. I never really liked ostarine. It makes me lethargic.

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Finished a 12-week ostarine (20 mg) daily 4 weeks ago. I lift weights 2 days a week and train Muay Thai 2-3 days a week. Happy with the results, I gained about 4 kg and some good strength. Ostarine appealed to me because it’s mild, has no back pumps or shoulder pumps, and I never felt shut down.

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Using 15 mg a day of ostarine at the moment, I am blown away by the strength gains and recomposition effects it’s had in as little as 30 days. Very easygoing on lipids too, which makes this my favorite SARM.

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Frequently Asked Questions

Can Ostarine Cause Bloating?

Several of our patients have reported bloating from ostarine. For some, this side effect ceased after a couple of weeks of supplementation, and for others, it persisted until cycle cessation.

Anti-estrogen medications can combat the following side effects of ostarine and other SARMs:

• Water retention
• Bloating
• Low testosterone
• Decreased spermatogenesis

Is 10 Milligrams of Ostarine Efficacious?

10 mg/day is the standard ostarine dosage utilized by females. This level is the lower end of the standard dosage for males. Such a dosage is likely to produce fewer side effects compared to larger dosages, with less pronounced anabolism and lipolysis.

What is the Price of Ostarine?

The price of ostarine can vary depending on the source. We find higher-quality products often cost more due to increased manufacturing costs and superior purity levels. Below is a list of current liquid ostarine prices:

• Sports Technology Labs: $54.99
• Chemyo: $69.99
• Pure Rawz: $75.95
• Behemoth Labz: $79.95

Is Ostarine Taken on an Empty Stomach?

Our patients have taken ostarine with and without food, and there appears to be no perceivable difference in regard to body composition changes.

When is the Most Optimal Time to Take Ostarine?

For some users, we have found that taking ostarine in the evening can increase the risk of insomnia. Thus, we typically administer ostarine in the morning and repeat this dosing every 24 hours.

What Duration is Required to Observe Results?

Results can typically be observed visually within the first 2 weeks of ostarine supplementation. Fluctuations in weight may not be a reliable indicator of results due to simultaneous muscle gain and fat loss.

Can Users Consume Ostarine Pre-Workout?

Some users administer ostarine pre-workout for increased intensity.

However, if the workout is in the evening and the user is susceptible to poor-quality sleep, they may benefit from not taking ostarine before exercise.

Equally, if a user commonly experiences dyspepsia, otherwise known as an upset stomach, after dosing, they may opt for a different time.

Can Ostarine Cause Diabetes?

Ostarine does not appear to cause diabetes in clinical literature or in our experience. Research indicates that ostarine can decrease fasting blood glucose by 11% (7).

Ostarine Pros and Cons

Pros:

• Fat burning
• Muscle building
• Strength enhancement

Cons:

• Some toxic effects
• Not as potent as other SARMs

Ostarine, or MK-2866, exhibits potent fat-burning properties attributed to its positive effects on insulin sensitivity and stimulation of the androgen receptor.

Results in terms of lean muscle are typically modest and widely considered to be inferior to those achieved with more potent SARMs, such as:

• LGD-4033
• RAD-140
• S23

Individuals often underestimate the severity of SARMs’ side effects. Even milder SARMs such as ostarine present toxicity in relation to the heart and liver. Testosterone suppression is also likely to occur, negatively affecting the HPTA.

Clomid can accelerate the recovery of the HPTA, according to Olson et al. (2012), shortening the period of low testosterone symptoms (8).

Ostarine vs. Anavar: What Are the Key Differences?

Anavar, an oral steroid, may pose fewer risks than ostarine, with several decades of medical research documenting its effects. However, Anavar exhibits similar side effects to ostarine in the following areas:

• Cholesterol alterations
• Raised liver enzymes
• Testosterone suppression

In previous research, the side effects from Anavar in therapeutic dosages have been unproblematic (9); hence, Anavar’s former FDA-approved status in medicine.

Despite the FDA’s removal of Anavar as a treatment for muscle wasting, we find Anavar’s risk-to-reward ratio to be more favorable than ostarine’s, as it can yield superior results in terms of:

• Fat loss
• Strength
• Muscle hypertrophy

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